Once chased through a wood by an armed swineherd from an enemy tribe. His hiding place spooked an old, gray, wild boar that made three great leaps at him – then disappeared; Cadoc took this as a sign, and the location became the site of the great church and monastery at Llancarvan, Wales; the house became renowned for the learning and holiness of its monks.

Legend says he once saved his brother monks in a famine by tying a white thread to the foot of a (well-fed) mouse; he then following the thread to an abandoned, well-stocked, underground granary. Another time he and his brothers went out to meet a band of thieves, chanting and playingharps; it surprised the highwaymen so much, they turned and left.